Performance of a Run-Around System for HVAC Heat and Moisture Transfer Applications Using Cross-Flow Plate Exchangers Coupled with Aqueous Lithium Bromide

A two-dimensional steady-state mathematical model is developed to study the heat and water vapor transport in a run-around heat and moisture exchanger coupled with a lithium bromide solution for air-to-air exchanger applications. A finite difference method is employed to solve the governing equations of the heat and moisture exchange, which gives the outlet air properties and effectiveness for selected operating conditions for each cross-flow exchanger. Using algorithms for the HVAC supply and exhaust exchangers coupled with a run-around liquid loop, the overall effectiveness of the run-around energy recovery system is shown to be dependent on the flow rate of both the pumped fluid and each airflow, the size and design of each exchanger, and the inlet operating conditions. It is shown that an overall effectiveness of 70% can be achieved when the run-around exchanger sizes and operating conditions are correctly chosen.

[1]  S. Kakaç,et al.  Heat Exchangers: Selection, Rating, and Thermal Design , 1997 .

[2]  R. Besant,et al.  Energy wheel effectiveness: part II—correlations , 1999 .

[3]  Refrigerating.  ASHRAE handbook of fundamentals , 1967 .

[4]  J. Niu,et al.  Effectiveness Correlations for Heat and Moisture Transfer Processes in an Enthalpy Exchanger With Membrane Cores , 2002 .

[5]  J. Whitelaw,et al.  Convective heat and mass transfer , 1966 .

[6]  Robert W. Besant,et al.  Reducing energy costs using run-around systems , 1995 .

[7]  R. Shah,et al.  Compact Heat Exchangers , 1990 .

[8]  Robert W. Besant,et al.  Determining the performance of energy wheels: Part 2 -- Experimental data and numerical validation , 1999 .

[9]  J. Niu,et al.  Membrane-based Enthalpy Exchanger: material considerations and clarification of moisture resistance , 2001 .

[10]  Robert E. Wilson,et al.  Fundamentals of momentum, heat, and mass transfer , 1969 .

[11]  Roger R. Riehl,et al.  Development of an experimental loop heat pipe for application in future space missions , 2005 .

[12]  Robert W. Besant,et al.  Determining the performance of energy wheels: Part 1 -- Experimental and numerical methods , 1999 .

[13]  R. Besant,et al.  Energy wheel effectiveness: part I—development of dimensionless groups , 1999 .

[14]  L. Cisternas,et al.  An analytic correlation for the vapour pressure of aqueous and non-aqueous solutions of single and mixed electrolytes. Part II. Application and extension , 1991 .

[15]  E. Schlunder.  Heat exchanger design handbook , 1983 .

[16]  John W. Mitchell,et al.  Performance of Rotary Heat and Mass Exchangers , 1995 .

[17]  Robert W. Besant,et al.  A Testing and HVAC Design Methodology for Air-to-Air Heat Pipe Heat Exchangers , 1998 .

[18]  R. Shah.  EXTENDED SURFACE HEAT TRANSFER , 2006 .

[19]  Ivan Dmitrievich Zaĭt︠s︡ev,et al.  Properties of Aqueous Solutions of Electrolytes , 1992 .

[20]  Frank P. Incropera,et al.  Fundamentals of Heat and Mass Transfer , 1981 .

[21]  Refrigerating.  2001 ASHRAE handbook : fundamentals , 2001 .

[22]  Carey J. Simonson,et al.  Heat and Moisture Transfer in Desiccant Coated Rotary Energy Exchangers: Part I. Numerical Model , 1997 .

[23]  Aliakbar Akbarzadeh,et al.  Application of heat pipe heat exchangers to humidity control in air-conditioning systems , 1997 .

[24]  Dusan P. Sekulic,et al.  Thermal Design Theory for Regenerators , 2007 .

[25]  D. P. Sekulic,et al.  Extended surface heat transfer , 1972 .

[26]  Robert W. Besant,et al.  Design of multi-coil run-around heat exchanger systems for ventilation air heating and cooling , 1995 .